1. Field of the Invention
The present invention is related to door lock mechanisms which are arranged to be electrically power locked or power unlocked.
2. Description of the Prior Art
Historically, electric locking devices have been loosely divided into two types. One is the electric dead bolt type designed specifically with that single function in mind. The other consists of standard mechanical locking hardware, modified to be operated electrically.
Electric dead bolt devices have faced some limitations in application because of their generally narrower scope of function. This is particularly true where building and safety codes call for free egress, panic egress, key override, or latched, but not locked status.
While these functions are readily available in mechanical locking hardware and can be preserved when electrical operation modifications are incorporated, the cost of the devices and the cost of their installation is significantly higher than that of their electric dead bolt counterparts. The additional costs arise from the special door preparations required for the modified lock cases, the addition and placement of wires in the door which connect to the lock, the necessity of special hinges to transfer the electrical circuits from the door to the door frame, and special preparation and wiring of the door frame to allow connection of the control circuits to the circuits from the door.
It is known to provide door locking mechanisms with electrically responsive dead-locking means. A means of this type is especially useful when the door locking means is required to be actuated from a remote location. Such an arrangement is seen in U.S. Pat. Nos. 4,132,439 issued Jan. 2, 1979, 3,521,921 of July 28, 1970 and in 4,099,752 of July 11, 1978. An early form of electrical operating means incorporated in a door locking mechanism is seen in U.S. Pat. No. 1,270,468 of June 25, 1918.